Ink-jet printing method, ink-jet printing apparatus, and program

ABSTRACT

A controller generates printing data to be printed by the printing nozzles of at least first and second adjacent printing nozzle arrays out of a plurality of printing nozzle arrays on the basis of tone information of image data to be printed. In particular, the controller generates printing data to be printed by each of the first and second printing nozzle arrays in the range in which the influence of an air flow generated along with ink discharge from the first and second printing nozzle arrays is admissible. Printing by the first and second printing nozzle arrays of the printhead is controlled on the basis of the generated printing data.

FIELD OF THE INVENTION

[0001] The present invention relates to an ink-jet printing method ofprinting on a printing medium by discharging ink from a printheadconstituted by arraying a plurality of ink discharge printing nozzlearrays.

BACKGROUND OF THE INVENTION

[0002] At present, OA devices such as a personal computer andwordprocessor have widely spread, and various printing apparatuses andprinting methods for printing information input by such OA device on aprinting medium have been developed. Particularly, more OA devicesprocess color information upon improvement of the information processingability. Along with this, printing apparatuses for outputtinginformation to be processed are shifting to color ones.

[0003] As a printing apparatus capable of forming a color image, thereare proposed various printing apparatuses in terms of the cost,function, and the like, including a low-cost printing apparatus having arelatively simple function and a multifunctional printing apparatuscapable of selecting the printing speed and image quality in accordancewith the type of image to be printed and the application.

[0004] In particular, ink-jet printing apparatuses have a feature ofeasily achieving low noise, low running cost, downsizing, and colorprinting. Such ink-jet printing apparatuses are widely used for aprinter, copying apparatus, facsimile apparatus, and the like.

[0005] Color ink-jet printing apparatuses generally print a color imageby using three, cyan, magenta, and yellow color inks, or four inksincluding black ink in addition to these inks.

[0006] Conventional ink-jet printing apparatuses generally use dedicatedpaper having an ink absorption layer as a printing medium in order toobtain a color image at high color development without any ink blur. Atpresent, printing apparatuses which have printing suitability for “plainpaper sheets” used in large quantities by a printer, copying apparatus,and the like upon improvement of ink are also put into practical use.

[0007] A printing means for printing in a plurality of colors such ascolor printing is a printhead in which printing nozzle arrays arearranged side by side. In this printhead, printing nozzle arrays(nozzles for use) for respective colors that are used for printing aresequentially arranged along the main scanning direction perpendicular tothe printing medium convey direction (sub-scanning direction). In singleprinting/scanning, ink droplets are discharged to the same raster fromnozzles.

[0008] A means for performing higher-image-quality printing in theink-jet printing apparatus using the side-by-side printhead ishigh-resolution printing. An effective means for this purpose is anarrangement using a high-density printhead in which the integrationdensities of printing elements and nozzles of the printhead areincreased. Recently, high-density printheads using a semiconductorprocess have been introduced. Printheads whose printing nozzle arrayshave a high density of 600 dpi (nozzle pit: about 42.3 μm) are alsomanufactured.

[0009] For higher densities, printheads in which a plurality of printingnozzle arrays are arranged parallel to each other and offset by apredetermined amount in the sub-scanning direction are alsomanufactured. For example, when the density of one printing nozzle arrayis 600 dpi, two printing nozzle arrays are arranged parallel to eachother, and offset at 1,200 dpi (nozzle pitch: about 21.2 μm) in thesub-scanning direction. This printhead can be used as a 1,200-dpihigh-density printhead.

[0010] Another means for printing at higher image quality issmall-droplet printing. To realize this, an arrangement using aprinthead in which the printing element and nozzle of a printhead aredownsized to discharge small droplets becomes effective. In recentyears, printheads capable of discharging small droplets at a dischargeamount of 4 to 5 pl are available. Printheads advantageous tohigh-resolution printing are also manufactured.

[0011] Higher-image-quality printing can be achieved using a printheadadvantageous to high-density printing, or a printhead capable ofdischarging small droplets advantageous to higher-resolution printing.

[0012] In the use of such printhead, however, the influence of inkdischarge from a plurality of printing nozzle arrays may appear. Sinceink droplets discharged from nozzles draw surrounding air, an aircurrent (air flow) is generated by movement of ink droplets upondischarging many ink droplets and at the same time, high-speed movementof the printhead. The air flow may directly influence discharge.

[0013] A mechanism of generating an air flow will be described indetail. Generation of an air flow corresponding to operation of theprinthead will be explained with reference to FIG. 1.

[0014]FIG. 1 is a plan view showing the discharge surface of theprinthead. Ink is discharged from a printing nozzle (not shown) in adirection perpendicular to the sheet surface. In FIG. 1, as theprinthead moves in the traveling direction (main scanning direction), itdischarges ink from the printing nozzles of printing nozzle array 1 toprint on a printing medium. At this time, an ink flow is generated byink discharge immediately below the printing nozzles, and acts as a “gaswall” which inhibits a gas flow. If the printhead moves in the travelingdirection in this state, an air current is generated behind the gaswall, and serves as an air flow (indicated by arrows in FIG. 1). Airthen flows behind printing nozzle array 1 in the traveling direction.This air flow may influence ink discharge from printing nozzle array 2.

[0015]FIG. 2 is a side view showing the printhead.

[0016] Similar to FIG. 1, as the printhead moves in the travelingdirection, it discharges ink from the printing nozzles of printingnozzle array 1 to print. An air current by an ink flow behind a gas wallwill be explained. As shown in FIG. 2, a downward air current (air flow)is generated by discharging ink, and the flow direction is changedbackward near a printing medium.

[0017]FIG. 3 is a front view showing the printhead in the travelingdirection.

[0018]FIG. 3 particularly depicts printing nozzle array 2 of theprinthead shown in FIG. 1 or 2. Similar to FIG. 1, as the printheadmoves in the traveling direction, it discharges ink from printingnozzles to print. Ink droplets from printing nozzles at the ends ofprinting nozzle array 2 are discharged inward near a printing mediumunder the influence of an air flow.

[0019] As a result, ink droplets discharged from printing nozzles nearthe two ends of printing nozzle array 2 land at positions shifted inwardfrom original landing positions on a printing medium, and are recognizedas an image error identical to a distortion or discharge failure. Thisimage error occurs because discharge of ink droplets from printingnozzles at ends shifts under the influence of an air flow flowing behinda gas wall described with reference to FIG. 1 and an air flow generatedby ink discharge described with reference to FIG. 2.

[0020] The influence of such air flow is strong when the distancesbetween a plurality of printing nozzle arrays of the printhead are shortand the printing nozzle arrays are close to each other. The influence isweak for a large ink volume, but strong for a small ink volume. Also,the influence is strong for a high printing nozzle density because thenumber of ink droplets which generate an air flow increases. Theinfluence is strong for a high moving speed of the printhead. Althoughthe degree of influence changes depending on the type of printhead, itsmoving speed, and ink discharge conditions, an air flow is generatedaround the printhead.

[0021] In a printing apparatus using a conventional printhead, an airflow occurs depending on the ink discharge state and printing conditionsof the printhead, degrading the quality of an image formed on a printingmedium. To solve this problem, complicated printing condition must beperformed, or control disadvantageous to printing operation must beperformed by excessively decreasing the moving speed of the printhead.

SUMMARY OF THE INVENTION

[0022] The present invention has been made to overcome the conventionaldrawbacks, and has as its object to provide an ink-jet printing methodcapable of suppressing an air flow generated around the printing nozzlearray of a printhead.

[0023] According to the present invention, the foregoing object isattained by providing an ink-jet printing method of printing on aprinting medium by discharging ink from a printhead constituted byarraying a plurality of printing nozzle arrays each formed by aplurality of printing nozzles for discharging ink, comprising:

[0024] a generation step of generating printing data to be printed byeach of at least first and second adjacent printing nozzle arrays out ofthe plurality of printing nozzle arrays on the basis of tone informationof image data to be printed;

[0025] and a printing step of printing by discharging ink to a pixel ofthe printing medium from the first and second printing nozzle arrays onthe basis of the printing data generated in the generation step,

[0026] wherein in the generation step, printing data corresponding toeach of the first and second printing nozzle arrays is generated in arange in which a sum of the number of dots to be printed by the firstprinting nozzle array and the number of dots to be printed by the secondprinting nozzle array does not exceed a predetermined number.

[0027] In a preferred embodiment, the predetermined number includes amaximum number of printing dots with which influence of an air flowgenerated along with ink discharge from the first and second printingnozzle arrays is admissible.

[0028] In a preferred embodiment, the first and second printing nozzlearrays are arranged via a common ink chamber.

[0029] In a preferred embodiment, in the generation step, printing datacorresponding to each of the first and second printing nozzle arrays isso generated as to relatively decrease the number of printing dots bythe second printing nozzle array as the number of printing dots by thefirst printing nozzle array relatively increases.

[0030] According to the present invention, the foregoing object isattained by providing an ink-jet printing method of printing on aprinting medium by discharging ink from a printhead constituted byarraying a plurality of printing nozzle arrays each formed by aplurality of printing nozzles for discharging ink, comprising:

[0031] a generation step of generating printing data to be printed byeach of at least first and second adjacent printing nozzle arrays out ofthe plurality of printing nozzle arrays; and

[0032] a printing step of printing by discharging ink to a predeterminedregion of the printing medium from the first and second printing nozzlearrays on the basis of the printing data generated in the generationstep,

[0033] wherein in the generation step, printing data to be printed inthe predetermined region by each of the first and second printing nozzlearrays is so generated as to suppress a sum of a printing ratio ofprinting by the first printing nozzle array and a printing ratio ofprinting by the second printing nozzle array to be not more than apredetermined ratio.

[0034] According to the present invention, the foregoing object isattained by providing an ink-jet printing method of printing on aprinting medium by discharging ink from a printhead constituted byarraying a plurality of printing nozzle arrays each formed by aplurality of printing nozzles for discharging ink, comprising:

[0035] a generation step of generating printing data to be printed byeach of at least first and second adjacent printing nozzle arrays out ofthe plurality of printing nozzle arrays; and

[0036] a printing step of printing by discharging ink to a predeterminedregion of the printing medium from the first and second printing nozzlearrays on the basis of the printing data generated in the generationstep,

[0037] wherein in the generation step, printing data to be printed inthe predetermined region by each of the first and second printing nozzlearrays is generated in a range in which influence of an air flowgenerated along with ink discharge from the first and second printingnozzle arrays is admissible.

[0038] In a preferred embodiment, the admissible range includes a rangein which a shift amount from an ideal landing position of a dot is lessthan half of a dot diameter regardless of the influence of an air flow.

[0039] According to the present invention, the foregoing object isattained by providing an ink-jet printing apparatus which prints on aprinting medium by discharging ink from a printhead constituted byarraying a plurality of ink discharge printing nozzle arrays,comprising:

[0040] generation means for generating printing data to be printed byeach of at least first and second adjacent printing nozzle arrays out ofthe plurality of printing nozzle arrays on the basis of tone informationof image data to be printed; and

[0041] control means for controlling printing by the first and secondprinting nozzle arrays on the basis of the printing data generated bythe generation means,

[0042] wherein the generation means generates printing datacorresponding to each of the first and second printing nozzle arrays ina range in which a sum of the number of dots to be printed by the firstprinting. nozzle array and the number of dots to be printed by thesecond printing nozzle array does not exceed a predetermined number.

[0043] In a preferred embodiment, the predetermined number includes amaximum number of printing dots with which influence of an air flowgenerated along with ink discharge from the first and second printingnozzle arrays is admissible.

[0044] In a preferred embodiment, the first and second printing nozzlearrays are arranged via a common ink chamber.

[0045] In a preferred embodiment, a first ink amount discharged from thefirst printing nozzle array by one discharge is different from a secondink amount discharged from the second printing nozzle array by onedischarge.

[0046] In a preferred embodiment, the first ink amount discharged fromthe first printing nozzle array by one discharge is larger than thesecond ink amount discharged from the second printing nozzle array byone discharge.

[0047] In a preferred embodiment, a first printing ratio by the firstprinting nozzle array is higher than a second printing ratio by thesecond printing nozzle array.

[0048] In a preferred embodiment, the generation means independentlygenerates printing data corresponding to the first and second printingnozzle arrays.

[0049] In a preferred embodiment, index processing of converting oneprinting data generated on the basis of the image data to be printedinto printing data for the plurality of printing nozzle arrays isperformed.

[0050] In a preferred embodiment, the first and second printing ratiosare set different from each other in each printing mode.

[0051] In a preferred embodiment, the first and second printing nozzlearrays discharge the same type of ink.

[0052] In a preferred embodiment, the first and second printing nozzlearrays discharge different types of inks.

[0053] According to the present invention, the foregoing object isattained by providing an ink-jet printing apparatus which prints on aprinting medium by discharging ink from a printhead constituted byarraying a plurality of printing nozzle arrays each formed by aplurality of printing nozzles for discharging ink, comprising:

[0054] generation means for generating printing data to be printed byeach of at least first and second adjacent printing nozzle arrays out ofthe plurality of printing nozzle arrays; and

[0055] printing control means for printing by discharging ink to apredetermined region of the printing medium from the first and secondprinting nozzle arrays on the basis of the printing data generated bythe generation means,

[0056] wherein the generation means generates printing data to beprinted in the predetermined region by each of the first and secondprinting nozzle arrays in a range in which influence of an air flowgenerated along with ink discharge from the first and second printingnozzle arrays is admissible.

[0057] In a preferred embodiment, the admissible range includes a rangein which a shift amount from an ideal landing position of a dot is lessthan half of a dot diameter regardless of the influence of an air flow.

[0058] According to the present invention, the foregoing object isattained by providing a program which controls an ink-jet printingapparatus which prints on a printing medium by discharging ink from aprinthead constituted by arraying a plurality of ink discharge printingnozzle arrays, comprising:

[0059] a program code for a generation step of generating printing datato be printed by each of at least first and second adjacent printingnozzle arrays out of the plurality of printing nozzle arrays on thebasis of tone information of image data to be printed,

[0060] wherein in the program code for the generation step, printingdata to be printed in a pixel by each of the first and second printingnozzle arrays is generated in a range in which a sum of the number ofdots to be printed by the first printing nozzle array and the number ofdots to be printed by the second printing nozzle array does not exceed apredetermined number.

[0061] In a preferred embodiment, the program runs in a host apparatuswhich supplies printing data to the ink-jet printing apparatus.

[0062] Other features and advantages of the present invention will beapparent from the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate embodiments of theinvention, and together with the description, serve to explain theprinciples of the invention.

[0064]FIG. 1 is a plan view showing the discharge surface of a printheadfor explaining generation of an air flow by ink discharge;

[0065]FIG. 2 is a side view showing the printhead for explaininggeneration of an air flow by ink discharge;

[0066]FIG. 3 is a front view showing the printhead in the travelingdirection for explaining generation of an air flow by ink discharge;

[0067]FIG. 4 is a graph showing the printing ratios of a plurality ofprinting nozzle arrays of a printhead applicable to each embodiment ofthe present invention;

[0068]FIG. 5 is a perspective view schematically showing the arrangementof the main part of an ink-jet printing apparatus according to the firstembodiment of the present invention;

[0069]FIG. 6 is a perspective view schematically showing the structureof the main part of the ink discharge portion of the printhead accordingto the first embodiment of the present invention;

[0070]FIG. 7 is a block diagram showing the schematic arrangement of thecontrol circuit of the ink-jet printing apparatus according to the firstembodiment of the present invention;

[0071]FIG. 8 is a graph showing an example of printing dot control forcontrolling an air flow when printing is done in each pixel by twoneighboring printing nozzle arrays according to the first embodiment ofthe present invention;

[0072]FIG. 9 is a view showing an example of the arrangement of theprinting nozzle arrays of the printhead according to the firstembodiment of the present invention;

[0073]FIG. 10 is a view showing an example of the arrangement of dotswhich form one pixel by using the printhead according to the firstembodiment of the present invention;

[0074]FIG. 11 is a table showing an example of index control accordingto the first embodiment of the present invention;FIG. 12 is a graphshowing an example of printing dot control for controlling an air flowin 4-pass printing and 6-pass printing according to the first embodimentof the present invention;

[0075]FIG. 13 is a view showing an example of the arrangement of theprinting nozzle arrays of a printhead according to the second embodimentof the present invention;

[0076]FIG. 14 is a graph showing an example of printing dot control forcontrolling an air flow when printing is done by two neighboringprinting nozzle arrays according to the second embodiment of the presentinvention;

[0077]FIG. 15 is a view showing an example of the arrangement of theprinting nozzle arrays of a printhead according to the third embodimentof the present invention;

[0078]FIG. 16 is a graph showing an example of printing dot control forcontrolling an air flow when printing is done by two neighboringprinting nozzle arrays in which large and small dots coexist accordingto the third embodiment of the present invention; and

[0079]FIG. 17 is a flow chart showing the schematic flow of processingof generating printing data for controlling printing dots, which isrealized in each embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0080] Preferred embodiments of the present invention will be describedin detail below with reference to the accompanying drawings.

[0081] The present invention can be applied to all devices usingprinting media (e.g., paper, cloth, leather, nonwoven fabric, OHP sheet,and metal). Examples of applied devices are office devices (e.g.,printer, copying apparatus, and facsimile), and industrial productiondevices.

[0082] A serial printer type ink-jet printing apparatus having aplurality of printheads will be exemplified as an embodiment of thepresent invention.

[0083] In an embodiment of the present invention, the printing ratios ofrespective printing nozzle arrays are acquired in a printhead having aplurality of printing nozzle arrays. The printing ratio of one printingnozzle array is set in accordance with that of another printing nozzlearray.

[0084] This can suppress an image error caused by an air flow generateddepending on the discharge state and printing conditions of theprinthead. The performance of the printhead can be maximized to realizeoptimal printing. That is, the present invention can provide an ink-jetprinting apparatus and ink-jet printing method capable of printingalmost free from any air flow by managing the printing ratios ofprinting nozzle arrays without complicated control.

[0085] An example of printing control will be explained with referenceto FIG. 4.

[0086] One factor which determines whether an air flow occurs or not isthe distance between adjacent printing nozzle arrays. For example, anair flow hardly occurs when the distance is a pixel interval of 600 dpifor 20 pixels or more, but may occur for 10 pixels or less. Generationof an air flow changes depending on the printing conditions of theprinthead such as the printhead performance, the ink discharge amountper operation, and ink discharge conditions.

[0087] The present invention realizes printing control capable ofsuppressing an air flow in consideration of the printing conditions ofthe printhead.

[0088]FIG. 4 is a graph showing the printing ratios of a plurality ofprinting nozzle arrays of a printhead applicable to each embodiment ofthe present invention.

[0089]FIG. 4 shows a printing ratio management table in which theabscissa represents the printing ratio of printing nozzle array 1 andthe ordinate represents the printing ratio of printing nozzle array 2determined in accordance with that of printing nozzle array 1 in aprinthead having printing nozzle array 1 and printing nozzle array 2arranged parallel to it in the main scanning direction.

[0090] The printing ratio is defined as 100% when ink is discharged fromall the printing nozzles of printing nozzle array 1 out of the printingnozzle arrays of the printhead, thereby printing in the entire printingregion to be printed by one scanning of the printhead. Alternatively,the printing ratio is defined as 100% when data is printed in the entireprinting region which can be printed by one scanning by one printingnozzle array of the printhead per unit time. However, the definition ofthe printing ratio is not limited to them, and may be properlydetermined in accordance with the application and purpose.

[0091] In FIG. 4, when printing is done in discharge amount A, aprinting ratio control line 401 which makes the discharge amount pernozzle equal between printing nozzle array 1 and printing nozzle array 2is set. In this case, as the printing ratio of printing nozzle array 1increases, that of printing nozzle array 2 decreases. Their printingratios have an almost linear relationship.

[0092] A region above the printing ratio control line 401, i.e., regionwhere the sum of the printing ratios of printing nozzle array 1 andprinting nozzle array 2 is large is set as an NG region where theinfluence of an air flow is strong and the quality of an image formed ona printing medium is low. A region below the printing ratio control line401, i.e., region where the sum of the printing ratios of printingnozzle array 1 and printing nozzle array 2 is small is set as an OKregion where the influence of an air flow is weak and the quality of animage formed on a printing medium is high. In printing control, printingis set to be executed using the OK region.

[0093] When printing is done in discharge amount B, a printing ratiocontrol line 402 which makes the discharge amount per nozzle of printingnozzle array 2 about half that of printing nozzle array 1 is set. Alsoin this case, as the printing ratio of printing nozzle array 1increases, that of printing nozzle array 2 decreases. Their printingratios do not have any linear relationship, and the printing ratio ofprinting nozzle array 2 cannot be increased under strong influence ofthe printing ratio of printing nozzle array 1.

[0094] Also in this case, a region above the printing ratio control line402, i.e., region where the sum of the printing ratios of printingnozzle array 1 and printing nozzle array 2 is large is set as an NGregion where the influence of an air flow is strong and the quality ofan image formed on a printing medium is low. A region below the printingratio control line 402, i.e., region where the sum of the printingratios of printing nozzle array 1 and printing nozzle array 2 is smallis set as an OK region where the influence of an air flow is weak andthe quality of an image formed on a printing medium is high. In printingcontrol, printing is set to be executed using the OK region.

[0095] The first printing ratio of printing nozzle array 1 is preferablyhigher than the second printing ratio of printing nozzle array 2. Eachprinting ratio is determined on the basis of tone information of imagedata to be printed. The printing ratio may also be determined on thebasis of the printing mode (e.g., high-image-quality printing mode orhigh-speed printing mode).

First Embodiment

[0096] The first embodiment is related to ink-jet printing thatdischarges ink onto a printing medium from the nozzles of a printheadhaving a plurality of printing nozzle arrays. Particularly in the firstembodiment, the influence of an air flow by ink discharge is suppressedby controlling the numbers of dots to be discharged from a plurality ofneighboring printing nozzle arrays.

[0097] In the following drawings, the same reference numerals denote thesame or corresponding parts.

Arrangement of Printing Apparatus

[0098]FIG. 5 is a perspective view schematically showing the arrangementof the main part of an ink-jet printing apparatus according to the firstembodiment of the present invention.

[0099] In an ink-jet printing apparatus 1000 of FIG. 5, a printhead 1having a plurality of (four) head cartridges 1A, 1B, 1C, and 1D isexchangeably mounted on a carriage 2. Each of the head cartridges 1A to1D has a connector for receiving a signal for driving the printhead 1.

[0100] In the following description, all or an arbitrary one of the headcartridges 1A to 1D will be simply referred to as the printhead 1.

[0101] The head cartridges 1A to 1D of the printhead 1 print withdifferent color inks. The head cartridges 1A to 1D house ink tanks whichstore different, cyan (C), magenta (M), yellow (Y), and black (Bk) inks.The head cartridges 1A to 1D are positioned and exchangeably mounted onthe carriage 2. The carriage 2 has a connector holder (electricalconnection portion) for transmitting a driving signal or the like to thehead cartridges 1A to 1D via connectors.

[0102] The carriage 2 is guided and supported in the moving directionalong a guide shaft 3 which is set in the apparatus main body in themain scanning direction. The carriage 2 is driven by a main scanningmotor 4 via a motor pulley 5, driven pulley 6, and timing belt 7, andthe position and movement of the carriage 2 are controlled.

[0103] A recovery portion 14 which performs recovery operation in orderto keep a good ink discharge state of the printhead 1 is arranged on theleft side of the apparatus main body. The recovery portion 14 comprisesink recovery portions 15 which recover ink discharged from the headcartridges 1A to 1D of the printhead 1, a cap (not shown) which caps theprinthead 1, a wiper 18 which wipes the ink discharge surface of theprinthead 1, and a suction pump 16 for sucking ink from the inkdischarge nozzle of the printhead 1 via a suction nozzle 27. The wiper18 is stored in a wiper storage portion 17 when not in use.

[0104] A printing medium 8 is conveyed (sheet feed) in the sub-scanningdirection by rotation of two pairs of convey rollers 9 and 10 and conveyrollers 11 and 12 via a position (printing portion) facing the orificesurface of the printhead 1.

[0105] The printing medium 8 is supported on its lower surface by aplaten (not shown) so as to form a flat printing surface at the printingportion. In this case, the head cartridges 1A to 1D of the printhead 1mounted on the carriage 2 are held such that their orifice surfacesproject from the carriage 2 and become parallel to the printing medium 8between the two pairs of convey rollers 9 and 10 and convey rollers 11and 12.

[0106] The printhead 1 is an ink-jet printing means for discharging inkby using heat energy, and comprises an electrothermal transducer forgenerating heat energy. The printhead 1 discharges ink from an orificeto print by using a change in pressure caused by growth and shrinkage ofbubbles by film boiling which is generated by heat energy applied by theelectrothermal transducer.

[0107] The structure of the main part of an ink discharge portion 13 ofthe printhead 1 will be explained with reference to FIG. 6.

[0108]FIG. 6 is a perspective view schematically showing the structureof the main part of the ink discharge portion of the printhead accordingto the first embodiment of the present invention.

[0109] In FIG. 6, a plurality of orifices 22 are formed at apredetermined pitch in an orifice surface 21 which faces the printingmedium 8 at a predetermined gap (about 0.5 to 2 [mm]). Eachelectrothermal transducer (heating resistance element or the like) 25for generating energy corresponding to an ink discharge amount isarranged along the wall surface of a corresponding channel 24 whichcommunicates a common liquid chamber 23 with each orifice 22.

[0110] In the first embodiment, the printhead 1 is mounted on thecarriage 2 such that the orifices 22 are aligned in a directionperpendicular to the scanning direction of the carriage 2. The printhead1 is constituted such that a corresponding electrothermal transducer 25is driven (energized) on the basis of printing data to film-boil ink inthe channel 24, and ink is discharged from the orifice 22 by thegenerated pressure.

[0111] The arrangement of the control circuit of the ink-jet printingapparatus 1000 will be described with reference to FIG. 7.

[0112]FIG. 7 is a block diagram showing the schematic arrangement of thecontrol circuit of the ink-jet printing apparatus according to the firstembodiment of the present invention.

[0113] In FIG. 7, a controller 100 is a main control unit, and comprisesa CPU 101 in the form of a microcomputer, a ROM 103 which stores variousprograms including a program for realizing processing executed in eachembodiment of the present invention (to be described later), variousprinting dot management tables, and other fixed data, and a RAM 105having an area for mapping image data, a work area, and the like. Thecontroller 100 functions as a printhead control unit.

[0114] A host apparatus 110 is an image data supply source (e.g., acomputer for creating and processing printing data, an image reader, ora digital camera). The host apparatus 110 exchanges image data, othercommands, status signals, and the like with the controller 100 via aninterface (I/F) 112.

[0115] Examples of the interface (I/F) 112 are a USB interface, parallelinterface, and IrDA interface.

[0116] The host apparatus 110 generates printing data for realizingprinting control by the controller 100 of the ink-jet printing apparatus1000, and controls output of printing data to the controller 100.Generation and output control of printing data are realized by adedicated program such as a printer driver installed in the hostapparatus 110, but may be realized by dedicated hardware which realizesprocessing executed by the dedicated program.

[0117] The host apparatus 110 comprises standard building components(e.g., a CPU, RAM, ROM, hard disk, external memory, network interface,display, keyboard, and mouse) which are mounted in a general-purposecomputer.

[0118] In the ink-jet printing apparatus 1000, an operation unit 120 isa set of switches for receiving an instruction input by the operator.The operation unit 120 comprises a power switch 122, a switch 124 fordesignating the start of printing, and a recovery switch 126 fordesignating activation of suction recovery.

[0119] A head driver 140 is a driver which drives the discharge heater25 of the printhead 1 in accordance with printing data or the like. Thehead driver 140 has a shift register which aligns printing data incorrespondence with the positions of the electrothermal transducers(discharge heaters) 25, a latch circuit which latches data at a propertiming, a logical circuit element which operates the discharge heater insynchronism with a driving timing signal, and a timing setting unitwhich properly sets the driving timing (discharge timing) for adjustinga dot formation position.

[0120] The printhead 1 has a sub-heater 142. The sub-heater 142 performstemperature adjustment for stabilizing the ink discharge characteristic.The sub-heater 142 can be formed on a printhead board at the same timeas the discharge heater 25 and/or attached to the main body of theprinthead 1 or the head cartridges 1A to 1D.

[0121] A motor driver 150 is a driver which drives a main scanning motor152. A sub-scanning motor 162 is a motor used to convey (sub-scan) theprinting medium 8. A motor driver 160 is a driver which drives thesub-scanning motor 162.

[0122] Printing dot control executed by the ink-jet printing apparatus1000 of the first embodiment in order to control an air flow generatednear the printing nozzle array will be explained.

Air Flow Control

[0123]FIG. 8 is a graph showing an example of printing dot control forcontrolling an air flow when printing is done in each pixel by twoneighboring printing nozzle arrays according to the first embodiment ofthe present invention. The two printing nozzle arrays (first and secondprinting nozzle arrays) are arranged adjacent to each other in the mainscanning direction different from the nozzle array direction.

[0124]FIG. 8 shows a printing dot management table for controlling thenumber of printing dots of printing nozzle array 2 depending on that ofprinting nozzle array 1 in accordance with an air flow control line 801.A region above the air flow control line 801 of the printing dotmanagement table in FIG. 8 is an NG region where the influence of an airflow by ink discharge of printing nozzle array 1 is strong and thequality of an image on a printing medium is low. The numbers of printingdots of printing nozzle array 1 and printing nozzle array 2 controlprinting by using a region below the air flow control line 801, i.e., anOK region where the quality of an image on a printing medium is high.

[0125] In this specification, the NG region is defined as a region wherelanding from an end nozzle shifts under the influence of an air flow, asshown in FIG. 3, and an image error such as a distortion ornonuniformity occurs, i.e., a region where landing of a printing dotfrom printing nozzle array 2 shifts under the influence of an air flowcaused by ink discharge from printing nozzle array 1 in FIG. 8, causingan image error.

[0126] More specifically, the NG region is a region where a landingposition shift corresponding to one dot occurs between adjacent dots in1,200-dpi high-density printing using dots of about 30 μm. The shiftamount from the ideal landing position of one dot is measured during oneprinting/scanning. If the shift amount is about 15 μm and an adjacentdot similarly shifts by about 15 μm in the opposite direction, adjacentdots shift by a total of 30 μm, resulting in an image error.

[0127] From this, the NG region is a region where the shift amount fromthe ideal landing position of one dot is a distance equal to or morethan half of the dot diameter (diameter of one dot). To the contrary,the OK region is defined as a region where the influence of an air flowdoes not exist, or even under the influence of an air flow, an imageerror such as a distortion or nonuniformity does not occur. The OKregion is a region where the shift amount from the ideal landingposition of one dot is a distance less than half of the dot diameterwhen the shift amount from the ideal landing position of one dot ismeasured during one printing/scanning.

[0128] As a concrete example, 1,200-dpi high-density printing using dotsof about 30 μm has been described. The shift amount in the NG or OKregion is merely an example in multipass printing, e.g., 4-pass printingon special-purpose paper (trade name: Professional Photo Paper availablefrom Canon). The reference shift amount changes depending on conditionssuch as the printing density, the number of passes, and the printingmedium.

[0129] In this manner, according to the first embodiment, printing datafor printing nozzle array 1 and printing nozzle array 2 are generated inthe range in which the influence of an air flow generated along with inkdischarge from printing nozzle array 1 and printing nozzle array 2 isadmissible. The range in which the influence of an air flow isadmissible is the range of the OK region below the air flow control line801, in other words, a range in which the shift amount from the ideallanding position of a dot is a distance less than half of the dotdiameter regardless of the influence of an air flow.

[0130]FIG. 8 shows the number of printing dots for one pixel, and thesame control can also be performed even with the average number ofprinting dots in a plurality of pixels. The same control can also bedone using the printing ratio per unit time or the average number ofprinting dots in a printing pixel per unit time.

[0131]FIG. 9 is a view showing an example of the arrangement of theprinting nozzle arrays of the printhead according to the firstembodiment of the present invention.

[0132] In FIG. 9, while the printhead 1 moves in the travelingdirection, it prints by discharging ink of the same color from theprinting nozzles of printing nozzle array 1 and printing nozzle array 2.The positional relationship between printing nozzle array 1 and printingnozzle array 2 will be described. Nozzles are arrayed at an interval of600 dpi in each printing nozzle array, and printing nozzle array 1 andprinting nozzle array 2 are respectively arranged on the right and leftsides of the ink chamber. The position of printing nozzle array 2 isvertically shifted by 1,200 dpi from printing nozzle array 1 toconstitute the printhead 1 having a nozzle pitch of 1,200 dpi.

[0133]FIG. 10 is a view showing an example of the arrangement of dotswhich form one pixel by using the printhead according to the firstembodiment of the present invention.

[0134] In this case, one pixel is formed by zero to four dots. Note thatFIG. 10 illustrates a case wherein one pixel is formed by a maximumnumber of dots, i.e., four dots. More specifically, data in imageprocessing is processed at 600 dpi, and multilevel information isgenerated for one pixel. The ink-jet printing apparatus 1000 sets thenumber of dots to be printed by a plurality of nozzles corresponding toa target pixel on the basis of the multilevel information.

[0135] In FIG. 10, one pixel at 600 dpi is so formed as to allowprinting two dots in the vertical direction and two dots in thehorizontal direction. That is, an image is formed by a maximum number offour dots in one pixel. This is merely an example, and the number ofdots which form one pixel changes depending on the characteristics ofthe ink-jet printing apparatus 1000 and printhead 1.

[0136] Several methods of realizing printing dot control will bedescribed.

[0137] A case wherein printing data for controlling a printing dot isgenerated in the host apparatus 110 will be explained.

[0138] In this case, the printer driver generates printing data ofbinary or multilevel information printable by the ink-jet printingapparatus 1000 on the basis of image data which is generated by anapplication running in the host apparatus 110 and is to be printed. Inthe printer driver, target image data is processed for each pixel. Theprinter driver independently generates printing data corresponding toprinting nozzle array 1 and printing nozzle array 2.

[0139] More specifically, when printing data is to be generated for eachpixel, printing dots for expressing the pixel are determined on thebasis of the air flow control line 801 in FIG. 8. For example, whenthree printing dots are necessary to express the tone of a given pixel,a combination of three printing dots is selected within the OK regionbelow the air flow control line 801 from printing dots to be dischargedfrom printing nozzle array 1 and printing nozzle array 2.

[0140] In FIG. 8, a combination of three printing dots in the OK regionbelow the air flow control line 801 is made up of, e.g., two dots fromprinting nozzle array 1 and one dot from printing nozzle array 2. Inaddition to this, any combination of three printing dots can be selectedwithin the OK region below the air flow control line 801.

[0141] Printing data corresponding to each of printing nozzle array 1and printing nozzle array 2 is generated in a range in which the sum ofthe number of dots to be printed by printing nozzle array 1 and thenumber of dots to be printed by printing nozzle array 2 adjacent toprinting nozzle array 1 does not exceed a predetermined number (numberof dots along the air flow control line 801). Image data correspondingto a plurality of printing nozzle arrays capable of suppressing an airflow generated between printing nozzle array 1 and printing nozzle array2 can be independently generated.

[0142] The predetermined number corresponds to the number of dots on theair flow line 801, and is a maximum number of printing dots with whichthe influence of an air flow generated along with ink discharge fromprinting nozzle array 1 and printing nozzle array 2 is admissible.

[0143] Various combinations of printing dots are conceivable as far asthey fall within the OK region determined by the air flow control lineof the printing dot management table. In terms of suppressing an airflow, the first ink amount (number of dots) discharged from printingnozzle array 1 by one discharge and the second ink amount (number ofdots) discharged from printing nozzle array 2 by one discharge arepreferably different from each other. In addition, the first ink amountis preferably larger than the second one.

[0144] A case wherein the ink-jet printing apparatus 1000 generatesprinting data for controlling printing dots, on the basis of image datawhich is generated by the host apparatus 110 and is to be printed willbe described. Index control will be explained as an example ofgenerating printing data for controlling printing dots by the ink-jetprinting apparatus 1000.

[0145] In index control, a plurality of combinations of printing dotsare generated from one multilevel information (tone information) toexpress the tone of one pixel. FIG. 11 shows an example of indexcontrol. Similar to FIG. 10, one pixel is so formed as to allow printinga total of four dots, i.e., two dots in the vertical direction and twodots in the horizontal direction. Printing dots have two, large andsmall sizes, a large dot is represented by 5 ng, and a small dot isrepresented by 2 ng. Image data of multilevel information received fromthe host apparatus 110 is 3-bit, i.e., eight-valued tone information(eight gray levels from Level 0 to 7). A combination of dots which formone pixel is determined in accordance with the tone information (Level 0to 7).

[0146] In FIG. 11, as the gray level increases, small dots are firstadded one by one, and then large dots replace small dots, expressingeight gray levels without degrading the tone quality.

[0147] Assuming that dots printed by printing nozzle array 1 in FIG. 8or 9 are large dots and dots printed by printing nozzle array 2 aresmall dots, large and small dots are used in the OK region below the airflow control line 801 of FIG. 8 in an example of index control shown inFIG. 11. In other words, in index control, a combination of printingdots to be discharged from printing nozzle array 1 and printing nozzlearray 2 can be determined while satisfying the OK region below the airflow control line 801 of the printing dot management table in FIG. 8,i.e., realizing air flow control. Even in index control, printing datacorresponding to each of printing nozzle array 1 and printing nozzlearray 2 can be generated in a range in which the sum of the number ofdots to be printed by printing nozzle array 1 and the number of dots tobe printed by printing nozzle array 2 does not exceed a predeterminednumber (number of dots along the air flow control line 801).

[0148] A case wherein printing data for controlling printing dots isgenerated in the host apparatus 110 (method of generating independentprinting data for a plurality of printing nozzle arrays) and a case(index control) wherein printing data for controlling printing dots isgenerated in the ink-jet printing apparatus 1000 will be compared.

[0149] The former method is highly versatile, has a merit of realizingvarious combinations, and is effective for strict image generation. Thelatter method cannot provide various combinations of printing dots,obtains only simple combinations, but can reduce the image data amount.Which of the methods is used is determined in accordance with thefeature of the printing apparatus, and the same air flow control can beexecuted in the two methods.

[0150] Of the two printing data generation methods, the former isrealized by the host apparatus 110, and the latter is realized by theink-jet printing apparatus 1000. However, the present invention is notlimited to this, and the methods may be executed by at least either ofthe host apparatus 110 and ink-jet printing apparatus 1000 on the basisof various conditions such as the performance of the host apparatus 110,that of the ink-jet printing apparatus 1000, and the printing mode.Alternatively, processing contents may be distributed and cooperativelyexecuted between the two apparatuses.

[0151] An example of air flow control in multipass printing in whichprinting is completed by scanning a predetermined printing region by theprinthead a plurality of number of times will be explained as amodification to air flow control.

[0152]FIG. 12 is a graph showing an example of printing dot control forcontrolling an air flow in 4-pass printing and 6-pass printing accordingto the first embodiment of the present invention.

[0153] Similar to FIG. 8, FIG. 12 shows an example of printing dotcontrol for controlling an air flow when printing is done in each pixelby two neighboring printing nozzle arrays. The number of printing dotsof printing nozzle array 1 and that of printing nozzle array 2 arecontrolled in accordance with air flow control lines 1201 and 1202.

[0154] In FIG. 12, a region above the 6-pass air flow control line 1201in 6-pass printing or a region above the 4-pass air flow control line1202 in 4-pass printing is an NG region where the influence of an airflow by ink discharge of printing nozzle array 1 is strong and thequality of an image on a printing medium is low. The number of printingdots of printing nozzle array 2 controls printing by using a regionbelow the 6-pass air flow control line 1201 in 6-pass printing or aregion below the 4-pass air flow control line 1202 in 4-pass printing,i.e., an OK region where the quality of an image on a printing medium ishigh.

[0155] Even if the same number of dots are printed in one pixel in4-pass printing and 6-pass printing, the printing ratio in oneprinting/scanning is different between them. More specifically, theprinting ratio of 6-pass printing is lower than that of 4-pass printing.In 6-pass printing in which printing is performed at a relatively lowprinting ratio, the influence of an air flow is weaker than in 4-passprinting, and the limit line of the air flow control line 1201 is sethigh to ensure a wide OK region. In this manner, the air flow controlcondition (air flow control line) is changed for each printing mode (4-or 6-pass printing), and control suitable for the printing mode can beexecuted.

[0156] As described above, according to the first embodiment, in ink-jetprinting of printing by discharging ink onto a printing medium from theprinting nozzles of a printhead having a plurality of printing nozzlearrays, the influence of an air flow by ink discharge can be suppressedby controlling for each pixel the numbers of dots to be discharged froma plurality of neighboring printing nozzle arrays. Control optimum forprinting using a plurality of printing nozzle arrays can be achieved torealize high-image-quality printing.

Second Embodiment

[0157] The second embodiment is related to ink-jet printing thatdischarges a plurality of types of inks onto a printing medium from theprinting nozzles of a printhead having a plurality of printing nozzlearrays. Especially in the second embodiment, the influence of an airflow by ink discharge is suppressed by controlling the numbers of dotsto be discharged from a plurality of neighboring printing nozzle arraysin printing with different inks.

[0158]FIG. 13 is a view showing an example of the arrangement of theprinting nozzle arrays of the printhead according to the secondembodiment of the present invention.

[0159] In FIG. 13, while a printhead having printing nozzle array 1 andprinting nozzle array 2 and a printhead having printing nozzle array 3and printing nozzle array 4 move in the traveling direction, theprintheads print by discharging ink from the printing nozzles ofprinting nozzle array 1 to printing nozzle array 4. In FIG. 13, twoprintheads identical to the printhead 1 in FIG. 9 are arranged side byside in the main scanning direction, and printing nozzles are arrayed atan interval of 600 dpi on the right and left sides of each ink chamber.The positions of the right and left printing nozzle arrays arevertically shifted by 1,200 dpi to constitute a printhead having anozzle pitch of 1,200 dpi.

[0160] The arrangement of dots which form one pixel is the same as thatin the first embodiment. As shown in FIG. 10, one pixel at 600 dpi isformed by a maximum number of two dots in the vertical direction and twodots in the horizontal direction, and an image is formed by a maximumnumber of four dots in one pixel.

[0161]FIG. 14 is a graph showing an example of printing dot control forcontrolling an air flow when printing is done in each pixel by twoneighboring printing nozzle arrays according to the second embodiment ofthe present invention.

[0162] In FIG. 14, the number of printing dots of printing nozzle array3 is controlled in accordance with that of printing nozzle array 2. Aregion above an air flow control line 1401 of FIG. 14 is an NG regionwhere the influence of an air flow by ink discharge of printing nozzlearray 2 is strong and the quality of an image on a printing medium islow. The number of printing dots of printing nozzle array 3 controlsprinting by using a region below the air flow control line 1401, i.e.,an OK region where the quality of an image on a printing medium is high.

[0163] With the arrangement of the printhead in FIG. 13, printing byprinting nozzle array 3 can be performed by printing nozzle array 4.Alternatively, printing nozzle array 1 may replace printing nozzle array2 in order to suppress ink discharge of printing nozzle array 2 thatgenerates an air flow.

[0164] In this example, attention is given to neighboring printingnozzle array 2 and printing nozzle array 3. The interval betweenprinting nozzle array 1 and printing nozzle array 4 is large, and noinfluence of an air flow appears. The influence of an air flow bydischarge of printing nozzle array 1 on printing nozzle array 3, andthat of an air flow by discharge of printing nozzle array 2 on printingnozzle array 4, or opposite influences can also be ignored.

[0165] From this, attention is given to the numbers of printing dots ofthe closest printing nozzle array 2 and printing nozzle array 3 in whichthe influence of an air flow is considered to be strong. In a regionwhere image degradation under the influence of an air flow is predicted,control is so executed as to use an alternative printing nozzle array.An image is formed in the OK region where the influence of an air flowis weak.

[0166] A method of generating printing data for controlling printingdots is the same as that in the first embodiment. Image data areindependently generated for printing nozzle array 2 and printing nozzlearray 3, or index control as shown in FIG. 11 is adopted.

[0167] Generation of image data for controlling printing dots targetsprinting nozzle array 2 and printing nozzle array 3, but may be executedfor printing nozzle array 1, printing nozzle array 2, printing nozzlearray 3, and printing nozzle array 4. That is, the design matterincludes proper generation of printing data for controlling printingdots for adjacent printing nozzle arrays in accordance with theapplication and purpose.

[0168] As described above, according to the second embodiment, inink-jet printing that discharges a plurality of types of inks onto aprinting medium from the nozzles of a printhead having a plurality ofprinting nozzle arrays, the influence of an air flow by ink dischargecan be suppressed by controlling for each pixel the numbers of dots tobe discharged from a plurality of neighboring printing nozzle arrays.Control optimum for printing using a plurality of printing nozzle arrayscan be achieved to realize high-image-quality printing.

Third Embodiment

[0169] The third embodiment is related to ink-jet printing thatdischarges ink onto a printing medium from the nozzles of a printheadhaving a plurality of printing nozzle arrays. Especially in the thirdembodiment, the influence of an air flow by ink discharge is suppressedby controlling for each pixel the numbers of dots to be discharged froma plurality of neighboring printing nozzle arrays by using a pluralityof printing nozzle arrays in which printing nozzles for discharging aplurality of ink amounts are arrayed.

[0170]FIG. 15 is a view showing an example of the arrangement of theprinting nozzle arrays of the printhead according to the thirdembodiment of the present invention.

[0171] In FIG. 15, while the printhead moves in the traveling direction,the printhead prints by discharging ink from the printing nozzles ofprinting nozzle array 1 and printing nozzle array 2. The positionalrelationship between printing nozzle array 1 and printing nozzle array 2will be described. Nozzles are arrayed at an interval of 600 dpi inprinting nozzle array 1 and printing nozzle array 2, and printing nozzlearray 1 and printing nozzle array 2 are respectively arranged on theright and left sides of the ink chamber.

[0172] Large- and small-dot printing nozzles are alternately arrayed inprinting nozzle array 1 and printing nozzle array 2. The positions oflarge- and small-dot printing nozzles are shifted in printing nozzlearray 1 and printing nozzle array 2. That is, the printhead isconstituted as a printhead having large and small dots at a nozzle pitchof 600 dpi.

[0173]FIG. 16 is a graph showing an example of printing dot control forcontrolling an air flow when printing is done in each pixel by twoneighboring printing nozzle arrays in which large and small dots coexistaccording to the third embodiment of the present invention.

[0174] In FIG. 16, the number of printing dots by small dots iscontrolled in accordance with that of printing dots by large dots. Aregion above an air flow control line 1601 of FIG. 16 is an NG regionwhere the influence of an air flow by ink discharge of large dots isstrong and the quality of an image on a printing medium is low. Thenumber of printing dots by small dots controls printing by using aregion below the air flow control line 1601, i.e., an OK region wherethe quality of an image on a printing medium is high.

[0175] A method of generating printing data for controlling printingdots is the same as that in the first embodiment. Image data areindependently generated for large and small dots, or index control asshown in FIG. 11 is adopted.

[0176] In the third embodiment, not an air flow is controlled for eachprinting nozzle array, but printing dots are controlled for eachprinting nozzle having a different discharge amount in a printing nozzlearray in which printing nozzles having different discharge amounts arealternately arrayed.

[0177] As described above, according to the third embodiment, in ink-jetprinting that discharges ink onto a printing medium from the nozzles ofa printhead having a plurality of printing nozzle arrays, the influenceof an air flow by ink discharge can be suppressed by controlling foreach pixel the numbers of dots to be discharged from a plurality ofneighboring printing nozzle arrays by using a plurality of printingnozzle arrays in which printing nozzles for discharging a plurality ofink amounts are arrayed. Accordingly, control optimum for printing usinga plurality of nozzles with a plurality of ink discharge amounts can beachieved to realize high-image-quality printing.

[0178] Processing of generating printing data for controlling printingdots, which is realized in each embodiment of the present invention,will be explained with reference to FIG. 17.

[0179]FIG. 17 is a flow chart showing the schematic flow of processingof generating printing data for controlling printing dots, which isrealized in each embodiment of the present invention.

[0180] For descriptive convenience, the first embodiment will beexemplified in FIG. 17. As for the second and third embodiments,processing realized by each embodiment can be executed by changing theprocessing target and conditions.

[0181] In step S101, image data to be printed is input.

[0182] “Input” means input of image data generated by the imageprocessing application of the host apparatus 110 to the printer driverwhen subsequent processing is executed by the printer driver in the hostapparatus 110. Also, “input” means input of image data generated by theimage processing application of the host apparatus 110 to the ink-jetprinting apparatus 1000 when subsequent processing is executed in theink-jet printing apparatus 1000.

[0183] Subsequent processing is realized by the printer driver or thecontroller 100 of the ink-jet printing apparatus 1000.

[0184] In step S102, tone information of image data is acquired. In stepS103, the printing dot management table is looked up on the basis of theacquired tone information.

[0185] In steps S104 and S105, a combination of printing dots to bedischarged from printing nozzle array 1 and printing nozzle array 2 thatsatisfies the OK region of the air flow control line of the printing dotmanagement table is determined by looking up the printing dot managementtable. Printing data corresponding to each printing nozzle array isgenerated.

[0186] In step S106, the generated printing dot is output to an outputdestination (ink-jet printing apparatus 1000 or head driver 140).

[0187] The above processing is merely an example. When index controldescribed in the first embodiment with reference to FIG. 11 is to beexecuted, a combination of large dots to be discharged from printingnozzle array 1 and small dots to be discharged from printing nozzlearray 2 is determined by looking up the printing dot management table onthe basis of tone information (Level 0 to 7) of image data in steps S104and S105. Printing data corresponding to each printing nozzle array isgenerated.

[0188] The same processing can also be performed by creating a table fordetermining printing dots to be discharged from printing nozzle array 1and printing nozzle array 2 for each gray level, and holding the tablein the printer driver or ink-jet printing apparatus 1000.

[0189] The present invention is particularly effective in, of ink-jetprinting systems, a printhead and printing apparatus of a system whichcomprises a means (e.g., an electrothermal transducer or laser beam) forgenerating heat energy as energy utilized to discharge ink and changesthe ink state by heat energy. This system can increase the printingdensity and resolution.

[0190] As a representative arrangement or principle, the presentinvention preferably adopts the basic principle disclosed in, e.g., U.S.Pat. Nos. 4,723,129 or 4,740,796.

[0191] This system is applicable to both a so-called on-demand apparatusand continuous apparatus. The system is particularly effective for theon-demand apparatus because of the following reason. That is, at leastone driving signal which corresponds to printing information and gives arapid temperature rise exceeding nuclear boiling is applied to anelectrothermal transducer arranged in correspondence with a sheet orliquid channel holding a liquid (ink). This signal causes theelectrothermal transducer to generate heat energy, and causes filmboiling on the heat effecting surface of the printhead. Consequently, abubble can be formed in the liquid (ink) in one-to-one correspondencewith the driving signal. Growth and shrinkage of the bubble dischargethe liquid (ink) from an orifice, forming at least one droplet. Thedriving signal more preferably has a pulse shape because a bubble growsand shrinks instantaneously at an appropriate timing to discharge theliquid (ink) with high response. The pulse-like driving signal ispreferably a signal disclosed in U.S. Pat. Nos. 4,463,359 or 4,345,262.Conditions disclosed in U.S. Pat. No. 4,313,124 which is an inventionconcerning the temperature rise ratio of the heat effecting surface canprovide higher-quality printing.

[0192] The printhead structure can be a combination (linear liquidchannel or right-angle liquid channel) of orifices, liquid channels, andelectrothermal transducers as those disclosed in the above-mentionedspecifications. The present invention also includes structures disclosedin U.S. Pat. Nos. 4,558,333 and 4,459,600 in which the heat effectingsurface is arranged in a bent region. The effects of the presentinvention are also effective for a structure based on Japanese PatentLaid-Open No. 59-123670 which discloses a structure in which a commonslit serves as the discharge portions of electrothermal transducers, anda structure based on Japanese Patent Laid-Open No. 59-138461 whichdiscloses a structure in which an opening for absorbing the pressurewave of heat energy corresponds to a discharge portion. In other words,the present invention can reliably, efficiently print regardless of theform of the printhead.

[0193] The present invention can also be effectively applied to a fullline type printhead having a length corresponding to the maximum widthof a printing medium printable by the printing apparatus. Such printheadmay take a structure which meets this length by a combination ofprintheads or a single integrated printhead structure.

[0194] The present invention is also effective in the use of theabove-described serial type printhead fixed to an apparatus main body,an interchangeable chip type printhead which can be electricallyconnected to an apparatus main body and receive ink from the apparatusmain body when attached to the apparatus main body, or a cartridge typeprinthead in which an ink tank is integrated with a printhead itself.

[0195] It is preferable to add a printhead recovery means or preliminarymeans to the printing apparatus because the effects of the presentinvention can then stabilize further. Practical examples of theadditional means are a capping means for the printhead, a cleaningmeans, a pressurizing or suction means, an electrothermal transducer,another heating element, a preliminary heating means as a combination ofthe electrothermal transducer and heating element, and a preliminarydischarge means which performs discharge unrelated to printing.

[0196] As for the type or number of mounted printheads, for example,only one printhead may be arranged in correspondence with a single colorink, or a plurality of printheads may be arranged in correspondence witha plurality of types of inks having different printing colors andconcentrations. For example, the printing mode of the printing apparatusmay use an integrated printhead or a plurality of printheads. Thepresent invention is very effective for an apparatus having at least oneof a printing mode in a plurality of different colors or a printing modein full color by color mixture.

[0197] The above embodiments of the present invention assume that ink isa liquid. It is also possible to use ink which solidifies at roomtemperature or more and softens or liquefies at room temperature. Ageneral apparatus performs temperature control such that the viscosityof ink falls within a stable discharge range by adjusting ink within therange of 30° C. (inclusive) to 70° C. (inclusive). Ink which liquefieswhen applied with a printing signal in use may be used. In order topositively prevent a temperature rise caused by heat energy by using thetemperature rise as energy of the state change from the solid state tothe liquid state of ink, or to prevent evaporation of ink, ink whichsolidifies when left to stand and liquefies when heated can be used. Inany case, the present invention is applicable to any ink which liquefiesonly when heat energy is applied, such as ink which liquefies whenapplied with heat energy corresponding to a printing signal and isdischarged as liquid ink, or ink which already starts to solidify whenarriving at a printing medium. As described in Japanese Patent Laid-OpenNo. 54-56847 or 60-71260, this type of ink can be held as a liquid orsolid in a recess or through hole in a porous sheet and opposed to anelectrothermal transducer in this state. In the present invention, it ismost effective to execute the aforementioned film boiling method foreach ink described above.

[0198] Furthermore, the ink-jet system according to the presentinvention may be used as an image output terminal for an informationprocessing device such as a computer. The ink-jet system may take theform of a copying apparatus combined with a reader, or a facsimileapparatus having a transmission/reception function.

[0199] The present invention is also achieved by supplying a softwareprogram (in the above embodiments, a program corresponding to the flowchart shown in FIG. 17) for realizing the functions of theabove-described embodiments to a system or apparatus directly or from aremote place, and reading out and executing the supplied program codesby the computer of the system or apparatus.

[0200] The present invention is therefore realized by program codesinstalled in the computer in order to realize functional processing ofthe present invention by the computer. That is, the present inventionincludes a computer program for realizing functional processing of thepresent invention.

[0201] In this case, the present invention can take any program formsuch as an object code, a program executed by an interpreter, or scriptdata supplied to an OS as long as a program function is attained.

[0202] A recording medium for supplying the program includes a floppy®disk, hard disk, optical disk, magnetooptical disk, MO, CD-ROM, CD-R,CD-RW, magnetic tape, nonvolatile memory card, ROM, and DVD (DVD-ROM andDVD-R).

[0203] As another program supply method, the program can be supplied byconnecting a client computer to an Internet homepage via the browser ofthe client computer, and downloading the computer program of the presentinvention or a compressed file containing an automatic installingfunction from the homepage to a recording medium such as a hard disk.The program can also be realized by grouping program codes whichconstitute the program of the present invention into a plurality offiles, and downloading the files from different homepages. That is, thepresent invention also includes a WWW server which allows a plurality ofusers to download the program files for realizing functional processingof the present invention by a computer.

[0204] The program of the present invention can be encrypted, stored ina recording medium such as a CD-ROM, and distributed to the user. A userwho satisfies predetermined conditions is caused to download decryptionkey information from a homepage via the Internet. The user executes theencrypted program by using the key information, and installs the programin the computer.

[0205] The functions of the above-described embodiments are realizedwhen the computer executes the readout program codes. Also, thefunctions of the above-described embodiments are realized when an OS orthe like running on the computer performs part or all of actualprocessing on the basis of the instructions of the program codes.

[0206] The functions of the above-described embodiments are realizedwhen the program read out from the recording medium is written in thememory of a function expansion board inserted into the computer or thememory of a function expansion unit connected to the computer, and theCPU of the function expansion board or function expansion unit performspart or all of actual processing on the basis of the instructions of theprogram codes.

[0207] As many apparently widely different embodiments of the presentinvention can be made without departing from the spirit and scopethereof, it is to be understood that the invention is not limited to thespecific embodiments thereof except as defined in the appended claims.

What is claimed is:
 1. An ink-jet printing method of printing on aprinting medium by discharging ink from a printhead constituted byarraying a plurality of printing nozzle arrays each formed by aplurality of printing nozzles for discharging ink, comprising: ageneration step of generating printing data to be printed by each of atleast first and second adjacent printing nozzle arrays out of theplurality of printing nozzle arrays on the basis of tone information ofimage data to be printed; and a printing step of printing by dischargingink to a pixel of the printing medium from the first and second printingnozzle arrays on the basis of the printing data generated in thegeneration step, wherein in the generation step, printing datacorresponding to each of the first and second printing nozzle arrays isgenerated in a range in which a sum of the number of dots to be printedby the first printing nozzle array and the number of dots to be printedby the second printing nozzle array does not exceed a predeterminednumber.
 2. The method according to claim 1, wherein the predeterminednumber includes a maximum number of printing dots with which influenceof an air flow generated along with ink discharge from the first andsecond printing nozzle arrays is admissible.
 3. The method according toclaim 1, wherein the first and second printing nozzle arrays arearranged via a common ink chamber.
 4. The method according to claim 1,wherein in the generation step, printing data corresponding to each ofthe first and second printing nozzle arrays is so generated as torelatively decrease the number of printing dots by the second printingnozzle array as the number of printing dots by the first printing nozzlearray relatively increases.
 5. An ink-jet printing method of printing ona printing medium by discharging ink from a printhead constituted byarraying a plurality of printing nozzle arrays each formed by aplurality of printing nozzles for discharging ink, comprising: ageneration step of generating printing data to be printed by each of atleast first and second adjacent printing nozzle arrays out of theplurality of printing nozzle arrays; and a printing step of printing bydischarging ink to a predetermined region of the printing medium fromthe first and second printing nozzle arrays on the basis of the printingdata generated in the generation step, wherein in the generation step,printing data to be printed in the predetermined region by each of thefirst and second printing nozzle arrays is so generated as to suppress asum of a printing ratio of printing by the first printing nozzle arrayand a printing ratio of printing by the second printing nozzle array tobe not more than a predetermined ratio.
 6. An ink-jet printing method ofprinting on a printing medium by discharging ink from a printheadconstituted by arraying a plurality of printing nozzle arrays eachformed by a plurality of printing nozzles for discharging ink,comprising: a generation step of generating printing data to be printedby each of at least first and second adjacent printing nozzle arrays outof the plurality of printing nozzle arrays; and a printing step ofprinting by discharging ink to a predetermined region of the printingmedium from the first and second printing nozzle arrays on the basis ofthe printing data generated in the generation step, wherein in thegeneration step, printing data to be printed in the predetermined regionby each of the first and second printing nozzle arrays is generated in arange in which influence of an air flow generated along with inkdischarge from the first and second printing nozzle arrays isadmissible.
 7. The method according to claim 6, wherein the admissiblerange includes a range in which a shift amount from an ideal landingposition of a dot is less than half of a dot diameter regardless of theinfluence of an air flow.
 8. An ink-jet printing apparatus which printson a printing medium by discharging ink from a printhead constituted byarraying a plurality of ink discharge printing nozzle arrays,comprising: generation means for generating printing data to be printedby each of at least first and second adjacent printing nozzle arrays outof the plurality of printing nozzle arrays on the basis of toneinformation of image data to be printed; and control means forcontrolling printing by the first and second printing nozzle arrays onthe basis of the printing data generated by said generation means,wherein said generation means generates printing data corresponding toeach of the first and second printing nozzle arrays in a range in whicha sum of the number of dots to be printed by the first printing nozzlearray and the number of dots to be printed by the second printing nozzlearray does not exceed a predetermined number.
 9. The apparatus accordingto claim 8, wherein the predetermined number includes a maximum numberof printing dots with which influence of an air flow generated alongwith ink discharge from the first and second printing nozzle arrays isadmissible.
 10. The apparatus according to claim 8, wherein the firstand second printing nozzle arrays are arranged via a common ink chamber.11. The apparatus according to claim 8, wherein a first ink amountdischarged from the first printing nozzle array by one discharge isdifferent from a second ink amount discharged from the second printingnozzle array by one discharge.
 12. The apparatus according to claim 11,wherein the first ink amount discharged from the first printing nozzlearray by one discharge is larger than the second ink amount dischargedfrom the second printing nozzle array by one discharge.
 13. Theapparatus according to claim 8, wherein a first printing ratio by thefirst printing nozzle array is higher than a second printing ratio bythe second printing nozzle array.
 14. The apparatus according to claim8, wherein said generation means independently generates printing datacorresponding to the first and second printing nozzle arrays.
 15. Theapparatus according to claim 8, wherein index processing of convertingone printing data generated on the basis of the image data to be printedinto printing data for the plurality of printing nozzle arrays isperformed.
 16. The apparatus according to claim 13, wherein the firstand second printing ratios are set different from each other in eachprinting mode.
 17. The apparatus according to claim 8, wherein the firstand second printing nozzle arrays discharge the same type of ink. 18.The apparatus according to claim 8, wherein the first and secondprinting nozzle arrays discharge different types of inks.
 19. An ink-jetprinting apparatus which prints on a printing medium by discharging inkfrom a printhead constituted by arraying a plurality of printing nozzlearrays each formed by a plurality of printing nozzles for dischargingink, comprising: generation means for generating printing data to beprinted by each of at least first and second adjacent printing nozzlearrays out of the plurality of printing nozzle arrays; and printingcontrol means for printing by discharging ink to a predetermined regionof the printing medium from the first and second printing nozzle arrayson the basis of the printing data generated by said generation means,wherein said generation means generates printing data to be printed inthe predetermined region by each of the first and second printing nozzlearrays in a range in which influence of an air flow generated along withink discharge from the first and second printing nozzle arrays isadmissible.
 20. The apparatus according to claim 19, wherein theadmissible range includes a range in which a shift amount from an ideallanding position of a dot is less than half of a dot diameter regardlessof the influence of an air flow.
 21. A program which controls an ink-jetprinting apparatus which prints on a printing medium by discharging inkfrom a printhead constituted by arraying a plurality of ink dischargeprinting nozzle arrays, comprising: a program code for a generation stepof generating printing data to be printed by each of at least first andsecond adjacent printing nozzle arrays out of the plurality of printingnozzle arrays on the basis of tone information of image data to beprinted, wherein in the program code for the generation step, printingdata to be printed in a pixel by each of the first and second printingnozzle arrays is generated in a range in which a sum of the number ofdots to be printed by the first printing nozzle array and the number ofdots to be printed by the second printing nozzle array does not exceed apredetermined number.
 22. The program according to claim 21, wherein theprogram runs in a host apparatus which supplies printing data to theink-jet printing apparatus.